chÖÔng 4 coïc vaø ñaøo saâu trong ñaát yeáu baØi giaÛng a pr.dr. chaÂu ngoÏcaÅn

CHNG 4 Coc va ao sau trong at yeuBAI GIANG A Pr.Dr. CHAU NGOCAN

NH B LN LCH QU GII HN S DNG BAI GIANG A Pr.Dr. CHAU NGOCAN

NN B PH HOI THEO H MT TRTBAI GIANG A Pr.Dr. CHAU NGOCAN

BAI GIANG A Pr.Dr. CHAU NGOCAN

Deep excavationAO SAU Plight of Foundation Engineers There is no glory in the foundations.from Karl Terzaghi, 1951 Eagles commonly fly alone. They arecrows, daws, and starlings that flocktogether. from John Webster (15801625), Englishdramatist. Ferdinand, in The Duchess of Malfi, act 5, sc. 2.


Kim tra vic thi cng h mng su Tp trung vo cc vic chnh sau y :Kim tra phng n thi cng h mng t vic o, chn gi, chng,..Bin php bo v cng trnh gn v cng trnh ngm ( ng cp v thot nc, ng dy thng tin, cp in vv....);


The excavation at the Century Hotel is completed here. Supports consist of diagonal braces at the corners of the excavation; this keeps the central part of the excavation free of obstructions. BAI GIANG A Pr.Dr. CHAU NGOCAN

The floor of the excavation has been prepared for construction of a mat foundation. The ground surface is covered with a thin layer of concrete to prevent disturbance (loosening) of the native soils. Before placing this concrete cover, the native soils were carefully inspected for loose zones and either compacted or over-excavated if necessary. BAI GIANG A Pr.Dr. CHAU NGOCAN

Notice the steel H-piles that reinforce the deep-soil-mixed wall panels can be seen in the walls of the excavation. BAI GIANG A Pr.Dr. CHAU NGOCAN

Another view of the diagonal bracing and the preparations for the mat foundation. BAI GIANG A Pr.Dr. CHAU NGOCAN

A temporary steel frame structure was erected along one side of the excavation, and used as a working platform (e.g., see the red crane in the upper left corner of the photo). BAI GIANG A Pr.Dr. CHAU NGOCAN

Trm bm Nhiu lc - Th ngh o su 19,5m, c 7 h thanh chng (c tendeur)BAI GIANG A Pr.Dr. CHAU NGOCAN

thanh chng (c tendeur) hc kch yBAI GIANG A Pr.Dr. CHAU NGOCAN

Trm bm Nhiu lc - Th ngh ang o v 3 h thanh chng (c tendeur)BAI GIANG A Pr.Dr. CHAU NGOCAN

These photos were taken in 1999 during the deep excavation for the Four Seasons Hotel, located along Market Street in San Francisco, California. This approximately 70-foot-deep excavation is bounded by existing structures on three sides, including the high rise in the background and Bart on the street side. This side of the excavation exposes the basement walls for the adjacent building. BAI GIANG A Pr.Dr. CHAU NGOCAN

Diagonal braces are used to support the side of the excavation that borders Market Street, and the below-ground BART transit tubes. The excavation wall along the street side consists of reinforced concrete diaphragm wall constructed in-situ in overlapping panels before the excavation started. BAI GIANG A Pr.Dr. CHAU NGOCAN

A horizontal waler runs along the excavation wall (lower left). On the lower right, the reinforcing steel cage for a portion of the mat is nearly completed. The soil in the lower-central portion of the photo is a berm that has been left in-place to minimize wall movements. It will be excavated later to make room for completion of the mat. BAI GIANG A Pr.Dr. CHAU NGOCAN

The reinforcing steel cage for the mat foundation is nearly complete over the central portion of this end of the excavation. Concrete for this portion of the mat will be poured first. Inclined braces (rakers) will then be connected from the lowest waler on the wall (see above photo) to the central mat. Once the rakers are in-place, the soil against the toe of the wall will be excavated and construction of the mat completed. BAI GIANG A Pr.Dr. CHAU NGOCAN

The reinforced concrete mat will vary in thickness from 4 to 8 feet across the building footprint. BAI GIANG A Pr.Dr. CHAU NGOCAN

The connection between the diagonal struts and the horizontal waler beam have been detailed to allow for shimming (chm) and preloading of the struts. Preloading of the struts is completed before the excavation advances past the strut level, which reduces wall movements during the excavation. BAI GIANG A Pr.Dr. CHAU NGOCAN

The other end of the excavation bottom is being prepared for erection of the reinforcing cage for the mat. The ground surface is protected against disturbance by a thin layer of concrete. Notice that the surface is slightly lower over a square region in the central bottom of the photo. The mat will be thicker in this region, as it will support greater superstructure loads at this point. BAI GIANG A Pr.Dr. CHAU NGOCAN

Tiebacks were used to support this side of the excavation. This minimized obstructions in this end of the excavation. Tiebacks could not be used for other portions of the excavation because of underground structures adjacent to the site (e.g., Bart on the one side). BAI GIANG A Pr.Dr. CHAU NGOCAN

A track mounted drill rig is used to drill and install the tiebacks. BAI GIANG A Pr.Dr. CHAU NGOCAN

Install the tiebacks. BAI GIANG A Pr.Dr. CHAU NGOCAN

Tieback Load TestThis load test was performed as part of a demonstration at a 1997 conference in Utah. The hydraulic jack (red) pulls on the tieback, while a dial gage mounted on a tripod (on the left) measures the movement of the tieback.BAI GIANG A Pr.Dr. CHAU NGOCAN


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